1. Field of the Invention
The present invention relates a method and apparatus for generating link quality indicator (LQI) information in a multi-band orthogonal frequency division multiplexing ultra-wide band system (MB-OFDM UWB system), and more particularly, to a method and apparatus for generating LQI information necessary for constructing effective piconets for selecting a channel, controlling transmission power, and changing a data transmission rate mode.
This work party supported by the IT R&D program of MIC/ITA [2006-S-071-01, Development of UWB Solution for High Speed Multimedia Transmission].
2. Description of the Related Art
In general, a multi-band orthogonal division multiplexing ultra-wide band system (MB-OFDM UWB system) constructs a plurality of piconets for connecting a plurality of devices in a narrow space by using a very low transmission power and limited frequency resources. In order to minimize mutual interference and to transmit much data in limited environments, a control of a transmission power and a change of a data transmission rate mode are needed. Accordingly, in order to construct effective piconets, information on received signal levels has to be transmitted from a physical layer to a media access control layer (MAC layer). Thus, in an existing wireless system technique, there are following techniques for setting received signal strength indication (hereinafter, referred to as RSSI).
In Korean Unexamined Patent Application Publication No. 10-1998-057727, since the MB-OFDM UWB system is constructed with a RSSI generator for generating RSSI that is a voltage for representing strength of the received signal through a radio frequency, a reference voltage generator for generating a reference voltage, a comparator for comparing the voltage generated by the RSSI generator with the voltage generated by the reference voltage generator, when RSSI is high due to noise, a method of changing a reference voltage based on a transmission power is suggested in order to prevent errors.
In Korean Unexamined Patent Application Publication No. 10-2004-0060307, a method of considerably removing noise caused by text data signals transmitted to a portable device by allowing a fixed device to measure RSSI of signals transmitted from the portable device and changing a degree of modulation of the transmitted text data based on the strength of the measured RSSI is suggested.
In addition, in Korean Unexamined Patent Application Publication No. 10-2006-0045865, a method of changing a RSSI threshold for securing receiving of a signal based on a progress of noise power obtained by estimating a difference between the estimated receiving power and the currently set RSSI threshold as noise power, when there is an error by detecting an error from a received signal based on the currently set RSSI threshold, in a case where signal transmission environments are considerably changed.
As described above, in the existing techniques, a method of setting RSSI is suggested. The degree of modulation of transmitted data is controlled by using the set RSSI value. Selectively, the RSSI threshold value is changed in receiving the RSSI. An optimal RSSI threshold value is selected and set under noise environments. However, although CCA, RSSI, and LQI are suggested in the system standard, the existing techniques consider only RSSI setting except the LQI. In order to consider the LQI, hardware devices have to be added to the existing wireless system.